Sacrum

The sacrum is the large, triangular bone at the base of the spine, formed by five fused vertebrae, that connects the lumbar spine above to the coccyx below and forms the back wall of the pelvis on either side through the sacroiliac joints.

What your sacrum connects and why it's a common source of pain

Your sacrum sits at the structural junction between your spine and your pelvis, forming joints on both sides — the sacroiliac (SI) joints — where it meets the iliac bones of the pelvis. These joints are heavily reinforced by ligaments and don't move much, but the small, controlled movement they do allow is critical for transferring load between the trunk and the legs during walking, standing, and bending.

Sacral pain can come from the SI joint itself, from the ligaments supporting it, from the muscles of the lower back and pelvis that attach to the sacrum, or from the sacral nerve roots that exit through openings in the bone and supply the lower limbs and pelvic floor. It often produces a deep, aching pain across the lower back or buttock — sometimes one-sided — that's difficult to locate precisely and can be mistaken for lumbar disc pain or hip pathology.

Why sacrum and SI joint pain is often mislabeled

Sacroiliac joint dysfunction is one of the most frequently overlooked sources of low back pain because it doesn't show up reliably on standard imaging and its symptom pattern overlaps significantly with lumbar spine conditions. People are often treated for lumbar disc or facet problems for months before anyone looks carefully at the SI joint as a contributing source.

Why standard back treatments don't always reach the problem

Lumbar-focused physical therapy and spinal mobilization don't consistently address SI joint mechanics. A physical therapist experienced in pelvis and SI joint assessment can identify the specific provocative pattern and apply targeted techniques and exercises that actually address the sacrum and its surrounding structures.

How Sword Health can help

A physical therapist can assess the sacrum and SI joints specifically, differentiate them from other lumbar causes, and guide you through a targeted rehabilitation plan. Sword makes that specialist-level care available from home, without the frustration of repeated visits that don't reach the right diagnosis.